Katherine Mayfair, who left Wisteria Lane, returns with her daughter Dylan and her husband Adam in Fairview after many years. However, Julie tells Susan that Dylan is not the one for whom it is. Meanwhile, Susan learns that she is pregnant, and Mike begins to abuse painkillers. Lynette does not want her friends to know that she was ill with cancer and tries to hide it. Gaby begins an affair with Carlos behind her husband, Mayor Victor, not realizing what a dangerous man he is.

Desperate Housewives season 4 episodes list:

Episode #1:
Now You Know (air date: 2007-09-30)

The neighborhood is shocked when news about Edie's suicide attempt spreads though Fairview. Lynette battles with the effects of chemotherapy. After a decade of absence, Katherine Mayfair moves back to Wisteria Lane with her new husband and daughter in her late teens.

Bree informs the housewives of what she overheard in the Mayfair house. Stella makes some special brownies to help Lynette through chemotherapy. Susan throws a charades party for the whole neighborhood.

Edie is shocked when she receives some news at the gynecologist's office. At the baby shower Bree's friends throw her, Bree's ex-mother-in-law Phyllis discovers her pregnancy is a hoax. Finally, Wisteria Lane welcomes to the street a homosexual couple.

Bob & Lee's contemporary water sculpture in their front yard prompts the Wisteria Lane neighborhood association into action. Edie finds out about the affair that Carlos is having with Gaby. Also, John Rowland wants to rekindle his romance with Gaby.

This is the show's first Halloween episode. Edie Britt's biggest fear comes true when Carlos walks out on their relationship. Susan finds Mike's father, who was supposedly dead. Danielle goes into labor right in the middle of the Halloween party... and somebody has to deliver the baby.

Episode #7:
You Can't Judge A Book By Its Cover (air date: 2007-11-11)

Lynette's sisters Lydia and Lucy come to visit. While having dinner with Susan and Mike, Bree and Orson realize they share different views on whether their newborn baby should be circumcised. On a boat, Victor confronts Gaby about her affair with Carlos and she throws him into the ocean. Later, Bree informs Susan that she thinks Mike is addicted to drugs.

A mysterious stalker from Adam's past shows up on Wisteria Lane, and they have dinner. Detectives question Gabrielle about Victor's whereabouts. Danielle's baby puts stress on Bree and Orson's marriage. Lynette has a reunion with her long-lost stepfather, Glen. Susan notices Mike is behaving strangely.

Two weeks after the tornado, with Mike still in rehab, Mrs. Delfino gets a visit from her cousin Tim. Meanwhile, Bree desperately awaits to return to her own house. Gabrielle learns that Carlos' blindness is permanent. Katherine is unable to keep some of her secrets from the women of Wisteria Lane. Finally, a surprise wedding ceremony has its own share of secrets.

Gabrielle struggles with the reality of having a blind husband. Lynette is surprised when Rick Coletti shows up at the Scavo pizzeria. Bree and Katherine join forces to plan the Founders Day Ball. As part of his recovery, Mike asks a few people for forgiveness, and Orson starts sleepwalking.

Bree and Katherine decide to start a catering business together. Lynette tries to deny her feelings for Rick. Mike learns the truth about his nearly fatal accident. Carlos gets a seeing-eye dog. Dylan meets her estranged father.

Susan meets her ex-husband, Karl at a Lamaze class, and finds out that he has remarried and is having another child. Lynette learns who was responsible for starting the fire at Rick's restaurant. Bree wants Orson to turn himself in to the police. Meanwhile, Gabrielle rents a room to a hip artist, Ellie, who has a dark secret. Elsewhere, Dylan continues meeting with her father, Wayne, and Katherine decides to go spy on her.

Susan and Mike try to name their son. Lynette is arrested for supposedly attacking Kayla, and Tom must do what he can to save his family. Bree is being stalked by Orson, and when she meets with Reverend Green, the reverend tries to hit on her. In the meantime, Gabrielle is still helping the police trying to detain Ellie for dealing drugs. Finally, Katherine is visited by her ex-husband, Wayne.

After Katherine announces that she has to leave town, Bree is left responsible for catering Bob and Lee's wedding. Gabrielle finds $118,000 in Ellie's teddy bear. Susan realizes she will soon lose someone she loves. Katherine Mayfair's secrets are finally revealed, and several residents of Wisteria Lane are faced with deadly threats.